Potential DGA(Domain Generation Algorithm) detected via Repetitive Failures - Static threshold based (ASIM DNS Solution)

Status: available
Severity: medium
Time window: 10d
Group by: DNSQueryCount, SrcIpAddr
Source: github.com/Azure/Azure-Sentinel

This rule identifies clients with a high NXDomain count, which could be indicative of a DGA (cycling through possible C2 domains where most C2s are not live). An alert is generated when a new IP address is seen (based on not being seen associated with NXDomain records in prior 10-day baseline period). It utilizes ASIM normalization and is applied to any source that supports the ASIM DNS schema.

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1008` Fallback Channels, `T1568` Dynamic Resolution

Event coverage

Provider	Event	Title
Sysmon	Event ID 22	DNSEvent (DNS query)

Rule body kusto

id: 89ba52fa-96a7-4653-829a-ca49bb13336c
name: Potential DGA(Domain Generation Algorithm) detected via Repetitive Failures - Static threshold based (ASIM DNS Solution)
description: |
  'This rule identifies clients with a high NXDomain count, which could be indicative of a DGA (cycling through possible C2 domains where most C2s are not live). An alert is generated when a new IP address is seen (based on not being seen associated with NXDomain records in prior 10-day baseline period). It utilizes [ASIM](https://aka.ms/AboutASIM) normalization and is applied to any source that supports the ASIM DNS schema.'
severity: Medium
status: Available 
tags:
  - Schema: ASimDns
    SchemaVersion: 0.1.6
requiredDataConnectors: []
queryFrequency: 1d
queryPeriod: 10d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CommandAndControl
relevantTechniques:
  - T1568
  - T1008
query: |
  let threshold = 100;
  let lookback = 10d;
  let referenceendtime = 1d;
  let nxDomainDnsEvents = (stime: datetime, etime: datetime) {
    _Im_Dns(responsecodename='NXDOMAIN', starttime=stime, endtime=etime)
    | where DnsQueryTypeName in ("A", "AAAA")
    | where ipv4_is_match("127.0.0.1", SrcIpAddr) == False
    | where DnsQuery !contains "/" and DnsQuery contains "."
  };
  nxDomainDnsEvents (stime=ago(referenceendtime), etime=now())
  | summarize
    StartTimeUtc = min(TimeGenerated),
    EndTimeUtc = max(TimeGenerated),
    DNSQueryCount=dcount(DnsQuery)
    by SrcIpAddr
  | where DNSQueryCount > threshold
  // Filter out previously seen IPs
  | join kind=leftanti (nxDomainDnsEvents (stime=ago(lookback), etime=ago(referenceendtime))
    | summarize DNSQueryCount=dcount(DnsQuery) by SrcIpAddr, bin(TimeGenerated,1d)
    | where DNSQueryCount > threshold)
    on SrcIpAddr
  // Pull out sample NXDomain responses for those remaining potentially infected IPs
  | join kind = inner (nxDomainDnsEvents (stime=ago(lookback), etime=now())
    | summarize by DnsQuery, SrcIpAddr)
    on SrcIpAddr
  | summarize
    StartTimeUtc = min(StartTimeUtc),
    EndTimeUtc = max(EndTimeUtc),
    DNSQueries=make_list(DnsQuery, 100)
    by SrcIpAddr, DNSQueryCount
  | extend DNSQueryThreshold=threshold
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr
eventGroupingSettings:
  aggregationKind: AlertPerResult
customDetails:
  DNSQueries: DNSQueries
  DNSQueryThreshold: DNSQueryThreshold
  DNSQueryCount: DNSQueryCount
alertDetailsOverride:
  alertDisplayNameFormat: "[Static threshold] Potential DGA (Domain Generation Algorithm) originating from client IP: '{{SrcIpAddr}}' has been detected."
  alertDescriptionFormat: "Client has been identified with high NXDomain count which could be indicative of a DGA (cycling through possible C2 domains where most C2s are not live). This client is found to be communicating with multiple Domains which do not exist.\n\nDGA DNS query count baseline is: '{{DNSQueryThreshold}}'\n\nCurrent failed DNS query count from this client: '{{DNSQueryCount}}'\n\nDNS queries requested by this client inlcude: '{{DNSQueries}}'"
version: 1.0.2
kind: Scheduled

Stages and Predicates

Parameters

let threshold = 100;
let lookback = 10d;
let referenceendtime = 1d;

The stages below define let nxDomainDnsEvents (the rule's main pipeline source).

Stage 1: `source`

_Im_Dns

Stage 2: `where`

where DnsQueryTypeName in~ ("A", "AAAA")

Stage 3: `where`

where not (ipv4_is_in_range(SrcIpAddr, "127.0.0.1"))

Stage 4: `where`

where not (DnsQuery contains "/") and DnsQuery contains "."

The stages below run on nxDomainDnsEvents (the outer pipeline).

Stage 5: `summarize`

summarize DNSQueryCount, EndTimeUtc, StartTimeUtc by SrcIpAddr

Threshold: gt 100

Stage 6: `where`

where DNSQueryCount > 100

Stage 7: `join` (negated)

join kind=leftanti (...)

Stage 8: `join`

join kind=inner (...)

Stage 9: `summarize`

summarize DNSQueries, EndTimeUtc, StartTimeUtc by SrcIpAddr, DNSQueryCount

Stage 10: `extend`

extend DNSQueryThreshold

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`SrcIpAddr`	cidr_match	`127.0.0.1`
`DnsQuery`	contains	`/`
`DNSQueryCount`	gt	`100`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`DNSQueryCount`	gt	`100` transforms: `cased`
`DnsQuery`	contains	`.` corpus 2 (kusto 2)
`DnsQueryTypeName`	in	`A` transforms: `cased` `AAAA` transforms: `cased`

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`DNSQueries`	`summarize`
`DNSQueryCount`	`summarize`
`EndTimeUtc`	`summarize`
`SrcIpAddr`	`summarize`
`StartTimeUtc`	`summarize`
`DNSQueryThreshold`	`extend`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Potential DGA(Domain Generation Algorithm) detected via Repetitive Failures - Static threshold based (ASIM DNS Solution)

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `summarize`

Stage 6: `where`

Stage 7: `join` (negated)

Stage 8: `join`

Stage 9: `summarize`

Stage 10: `extend`

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

Potential DGA(Domain Generation Algorithm) detected via Repetitive Failures - Static threshold based (ASIM DNS Solution)

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: where

Stage 5: summarize

Stage 6: where

Stage 7: join (negated)

Stage 8: join

Stage 9: summarize

Stage 10: extend

Exclusions

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `summarize`

Stage 6: `where`

Stage 7: `join` (negated)

Stage 8: `join`

Stage 9: `summarize`

Stage 10: `extend`